But since current software and hardware technology cannot truly allow a player to choose any role and do exclusively things that are appropriate to that role, your definition is pretty well pointless. Full points for ivory tower accuracy, and yet completely devoid of real world application.

So basically here, something does not exist, therefore lets pretend it exists so to get a real world application… And not doingthat would be the ivory tower accuracy.

What about some real world application? If it does not exist, just do not pretend it exists.
Or is there some natural law forcing RPG to exist on computers?

And the defining elements of a B-52 are wings, props, and payload. None of the elements are unique nor exclusive, and yet, if I pulled the curtain off an unknown vehicle I bet you could tell me whether it was more like a car or a bomber based on those defining elements you're so scornful of.

Back to reality : cars with wings?
Oh, a bird flying through the skies. It has wings, and payload. Cant be a plane.
Jet fighter has wings, payload, no propeller. Must be a bird.